KR102363701B1 - Method and apparatus for monitoring capacitor bushings for a three-phase ac system - Google Patents

Abstract

A method for monitoring capacitor bushings (2a, 2b, 2c) for a three-phase alternating current system, wherein each capacitor bushing (2a, 2b, 2c) is connected to one of the main lines (5a, 5b, 5c) of the alternating current system. A method comprising a conductor 4 to which is connected, and a conductive lining 3 surrounding the conductor 4, the method comprising: - upper capacitances C0a, C0b, C0c for each capacitor bushing 2a, 2b, 2c and determining the lower capacitances C1a, C1b, C1c; - the measured voltages U1a, U1b, U1c appearing between the respective linings 3 and the ground potential 13 are detected in the respective capacitor bushings 2a, 2b, 2c; - determining the actual capacitances C0a', C0b', C0c' for each of the capacitor bushings 2a, 2b, 2c, wherein the actual capacitance is determined by the respective measured voltages U1a, U1b, U1c and the respective measured voltages U1a, U1b, U1c The measured voltages U1b, U1c, U1a of one of the remaining capacitor bushings 2a, 2b, 2c and the lower capacitances C1a, C1b, C1c, the lower capacitances C1b, C1c, C1a and the upper capacitance C0b, depending on C0c, C0a); - comparing the respective upper capacitances C0a, C0b, C0c with the respective actual capacitances C0a', C0b', C0c' for each capacitor bushing 2a, 2b, 2c; and - generating a monitoring signal according to the result of the capacitance comparison.

Description

METHOD AND APPARATUS FOR MONITORING CAPACITOR BUSHINGS FOR A THREE-PHASE AC SYSTEM

The present invention relates to a method and device for monitoring a capacitor bushing for a three-phase alternating current main.

DE 195 19 230 C1 describes a monitoring method and a monitoring device for a capacitor bushing for high voltage, the bushing having a tap for the component voltage between its capacitor linings. According to this known method, it is supplied to a detection device that monitors whether the component voltage changes, the change in the component voltage and time information thereon are stored, the time interval between at least two changes is detected, the frequency of the component voltage A corresponding fault signal is generated. Such a known device comprises a detection device by which the component voltage is monitored, a memory in which the change in the component voltage and time information therefor is recorded, a computing element for detecting the time interval between at least two changes, and a fault signal means for generating a disturbance signal proportional to the frequency of the component voltage change. The tap is guided through the measuring bushing and through the measuring line to the detection device. The tap supplies the component voltage in response to an image of a high voltage appearing inside the capacitor bushing.

Because the high voltage seen by the capacitor bushings can affect the measurement signal and fluctuate significantly, the measurement detected at the tap can fluctuate significantly. Therefore, reliable monitoring of the capacitor bushing is not guaranteed.

DE 100 37 432 A1 describes a method and a device for monitoring a capacitor bushing to which an electrically operating voltage is applied, in which a voltage divider is formed by means of a conductive lining. In this known method, at least one measurement of the electrical measurement variable is detected and stored by means of a measurement tap connected to the lining and by means of a ground potential, and the impedance between the measurement tap and the ground potential is changed after detection of the at least one measurement. and then at least one signal value of the measuring signal formed is detected and stored by means of the measuring tap and the ground potential, wherein the time interval between the instant of detection of the at least one measured value and the instant of detection of the at least one signal value is the interval between the two instants. When a characteristic variable that is determined such that a change that may occur in the operating voltage is negligible, and is compared with a predetermined target value based on the measured value and the signal value, is determined by quotient formation, and the characteristic variable deviates from the predetermined target value A report signal is formed indicating a failure of the capacitor bushing. In this known device, there is provided a lining and a measuring tap connected to the measuring device for detecting an electrical measuring variable, the impedance appearing between the measuring tap and the ground potential comprises an impedance structure associated with the switching device. The impedance structure has a fixed impedance connectable to and separable from the measurement tap using a switching device. The switching device is connected to the control device. In order to monitor the capacitor bushing, the impedance structure is initially in a first measuring state with the switching device open, and the fixed impedance is not connected to the measuring tap. In this first measurement state, a measurement of the electrical measurement variable is detected at a first instant and stored in the memory of the measurement device. In this specification, this measurement variable is the transition appearing in the measurement tab relative to the ground potential. In this measurement state of the impedance structure, an impedance is formed by the parallel circuit of the capacitance and the internal resistance of the measurement device. In this measurement state, the impedance is called the unaltered impedance. After the measurement variable is detected, the impedance structure enters the second measurement state. For this purpose, the control device is transitioned to the closed state by the switching device in a controlled manner. As a result, the fixed impedance is now electrically connected to the measuring tap in energization. Impedance is now formed from the capacitance, the internal resistance of the measuring device and a parallel circuit of fixed impedance. In this second measuring state, the signal value of the measuring signal being formed is now detected by the measuring device at a second instant and stored in a similar way. The measurement signal is the voltage that appears on the measurement tap relative to the ground potential. In this second measurement state, the impedance is called a modified impedance.

Because the operating voltage seen across the capacitor bushings affects the measurement signal and can fluctuate significantly, the measurement detected at the measurement tap fluctuates significantly. Therefore, reliable monitoring of the capacitor bushing is not guaranteed.

DE 36 01 934 C2 describes a structure of permanently monitored capacitor bushings in large transformers of three-phase current mains, which have three capacitor bushings each consisting of a winding body with an embedded capacitor lining, each with the last external It has a measuring terminal connected to the capacitor lining and an external flange capacitance between the last external capacitor lining and the grounded flange of each bushing. In this known capacitor bushing construction, the measuring terminals of the three capacitor bushings are each connected via individual trimming capacitors with a star point which can be set to ground potential, the measuring device being located between the star point and the ground potential. is placed on A measuring device is provided which is connected to a trigger device which switches off the entire structure when the capacitance of the capacitor lining is changed.

US 4 757 263 A describes the determination of capacitance values for monitoring the insulating properties of high voltage bushings.

It is an object of the present invention to create a method and a device for monitoring a capacitor bushing for a three-phase alternating current mains, which enables better monitoring.

This object is achieved by the claims of the independent claims. Advantageous developments are described in the dependent claims.

According to a first aspect, the present invention provides a method for monitoring capacitor bushings for three-phase alternating current mains, each capacitor bushing comprising a conductor connected to one of the main lines of the alternating current mains, said conductor A method comprising: a conductive lining surrounding the

- determining the upper capacitance (C0a, C0b, C0c) and the lower capacitance (C1a, C1b, C1c) for each capacitor bushing;

- the measured voltages U1a, U1b, U1c appearing between each lining and the ground potential are detected and/or measured at each capacitor bushing;

- determining for each capacitor bushing the actual capacitances C0a', C0b', C0c', wherein the actual capacitance is applied to each measured voltage and to each lower capacitance and to the measured capacitance of one of the remaining capacitor bushings. dependent on the voltage and the lower capacitance and the upper capacitance;

- for each capacitor bushing comparing the respective upper capacitance with the respective actual capacitance; and

- Proposes a capacitor bushing monitoring method, comprising the step of generating a monitoring signal according to the result of the capacitance comparison.

In the proposed method, the upper capacitance of the capacitor bushing and its actual capacitance in operation are compared with each other, which is also called capacitance comparison. If the actual capacitance changes, it can be determined that the corresponding capacitor bushing is damaged.

The proposed method uses the characteristic parameters and measurement parameters of the remaining capacitor bushings for actual monitoring. In this respect, the measured voltage, lower capacitance, upper capacitance and actual capacitance of the capacitor bushing and one of the other capacitor bushings are used. Thereby, of course, when monitoring a capacitor bushing connected to the main line associated with the capacitor bushing, the measured voltage together with at least partial compensation for fluctuations appearing on the main line and transmitted to the measured voltage via the capacitor bushing connected to the respective main line. Measurements can be made of tolerance for error when detecting , and a better statement of the condition of the capacitor bushing can be made.

The upper capacitance for each capacitor bushing can be defined as needed in any desired mode and manner as needed, for example, as the capacitance of a capacitor formed by each lining and each conductor and referred to herein as a top voltage capacitor. . The upper capacitance usually has a value between 300 and 600 pF.

Each capacitor bushing may be formed in any desired mode and manner according to need, including, for example, in particular the first mentioned lining and at least one additional lining disposed between the conductor and the first such lining. Let the mentioned linings represent the outermost linings. The upper capacitance may then be defined, for example, as the capacitance of a series circuit comprising capacitors, each of which is formed by a conductor with two adjacent linings and an innermost of the additional linings and is similarly upper It is formed by a capacitor called a voltage capacitor.

The lower capacitance of each capacitor bushing may be defined as needed and in any desired mode and manner, for example the capacitance of a parallel circuit, which is referred to herein as a lower voltage capacitor, and the parallel circuit is for example each a measuring device capable of detecting/measuring the measured voltage of Capacitors formed by conductive flanges with The bottom capacitance usually has a value between 1 μF and 5 μF, but other values if necessary, e.g. between 0.1 μF and 50 μF, or between 0.2 μF and 20 μF, or between 0.5 μF and 10 μF. can have Alternatively or additionally, each of these lower capacitances and at least one of the other lower capacitances may have the same or a different value. For example, the lower capacitance is 1:2:3, 1:2:4, 1:2:5, 1:3:5, 1:3:7, 1:3:9, 1:4:7 or 1 It can have a ratio of :4:9.

The monitoring signal may be formed as required and in any desired mode and manner, for example as an acoustic and/or optical and/or electronic signal.

Determining the upper capacitance for the capacitor bushing can be done in any desired mode and manner as required, for example by measuring preferably on an intact or fault-free capacitor bushing, or by looking at the data sheet of the capacitor bushing, or This can be done by setting it empirically, or by taking the value from an earlier cycle of the method. Alternatively or additionally, determining the at least one upper capacitance includes, for example, before, after or concurrently with determining at least one of the other upper capacitances and/or prior to determining the at least one lower capacitance; It may be performed after or simultaneously with and/or before, after or simultaneously with detecting the at least one measured voltage.

Determining the underlying capacitance for the capacitor bushing may be accomplished in any desired mode and manner as required, for example by measuring preferably in an intact or fault-free capacitor bushing, or by looking at the data sheet of the capacitor bushing, or This can be done by setting it empirically, or by taking the value from an earlier cycle of the method. Alternatively or additionally, determining the at least one lower capacitance includes, for example, before, after or concurrently with determining at least one of the other lower capacitances and/or prior to determining the at least one upper capacitance; It may be performed after or simultaneously with and/or before, after or simultaneously with detecting the at least one measured voltage.

Detecting the at least one measured voltage can be carried out in any desired mode and manner as required, for example before, after or preferably simultaneously with and/or at least one of the other measured voltages. The determination may be performed before, after or concurrently with the determination of the upper capacitance and/or before, after or simultaneously with the determination of the at least one lower capacitance.

From here,

- said mains voltages Ua, Ub, Uc are detected for each phase;

- the mains voltages are compared with each other;

- As a result of voltage comparison, if the main voltages differ from each other by less than a predetermined amount, the actual capacitance is calculated, the capacitance is compared, and the monitoring signal is generated.

This comparison of the mains voltage is also referred to herein as a voltage comparison, whereby it is possible to determine the moment when the actual monitoring - ie the calculation of the actual capacitance, the comparison of the capacitances and the generation of the monitoring signal - is particularly advantageous and desirable, since This is because the operation is not made difficult, hampered or even impossible to perform by the mains voltages differing from each other by more than a predetermined amount. Thus, a better statement of the state of the capacitor bushing can be made irrespective of fluctuations in the mains voltage during detection of the measured voltage and tolerance for measurement errors.

By taking the mains voltage into account, it becomes possible, for example, to detect a change over time in the voltage ratio (also called asymmetry), thus at least partially compensating for the corresponding deviation of the measured voltage measured at the capacitor bushing. This enables reliable monitoring of the capacitor bushings taking into account and evaluating differences and disturbances in the mains voltage.

Detecting the at least one mains voltage may be performed in any desired mode and manner as required, for example before, after or preferably simultaneously with the detection of at least one of the other mains voltages, and/or of the at least one upper capacitance after the determination, simultaneously or preferably before and/or after the determination of the at least one lower capacitance, simultaneously or preferably before and/or after the detection of the at least one measured voltage, simultaneously or preferably before can be performed on

The voltage comparison may be performed in any desired mode and manner as required, for example after, simultaneously or preferably before and/or after, simultaneously or preferably after the determination of the at least one upper capacitance and/or after the determination of the at least one capacitance. This may be carried out before and/or after the detection of the at least one measured voltage, simultaneously or preferably before. If, as a result of the voltage comparison, the mains voltages no longer differ from each other by more than a predetermined amount, preferably the determination of the upper capacitance and/or the determination of the lower capacitance and/or the detection of the measured voltage, and finally the calculation of the actual capacitance, the capacitance The operation of comparing them and generating the monitoring signal is performed.

If, as a result of the voltage comparison, the main voltages differ from each other by more than a predetermined amount, the operation of calculating the actual capacitance, comparing the capacitance, and generating the monitoring signal is not performed while a new cycle of the method is performed. Then, preferably, at least one of the determination of the upper capacitance and/or the determination of the lower capacitance and/or the detection of the measured voltage is not performed.

After generating the monitoring signal, a new next additional cycle of the method is preferably performed.

From here,

- RMS values (Uae, Ube, Uce) and/or peak values and/or amplitudes of the main voltages (Ua, Ub, Uc) are used for voltage comparison.

From here,

- error tolerances for voltage comparison UAB > 0, UBC > 0, UCA >0 are determined;

- voltage comparison

|Uae - Ube| ≤ UAB and |Ube - Uce| ≤ UBC and |Uce - Uae| It is performed in such a way that it checks whether ≤ UCA.

Each of these tolerance values UAB, UBC, and UCA may be determined in any desired mode and method as necessary, for example, 0.1%, 0.2%, 0.5% of the rated value of each main voltage (Uae, Ube, Uce) , 1%, 2%, 3%, 4%, 5%, 7%, 10%, 15%, 20%, 25%, 30%, 40%, or 50%. Each of these tolerance values and at least one other tolerance value may be the same as or different from each other.

From here,

- The actual capacitance of the first capacitor bushing is calculated according to the following equation,

where Ka = 1 or Ka = Ub/Ua or Ka = Ube/Uae; and/or

- The actual capacitance of the second capacitor bushing is calculated according to the following equation,

where Kb is Kb = 1 or Kb = Uc/Ub or Kb = Uce/Ube; and/or

- The actual capacitance of the third capacitor bushing is calculated according to the following equation,

where Kc is a correction value such that Kc = 1 or Kc = Ua/Uc or Kc - Uae/Uce.

The second alternative, thus a correction to which the quotient of the two mains voltages is applied, allows and enables automatic correction and/or automatic compensation of the asymmetry and/or the difference between these two mains voltages. . This allows a more precise determination of the corresponding actual capacitance.

Each of these corrections may be selected as desired as desired. If, for example, in each example the first alternative is chosen for the correction so that Ka = Kb = Kc = 1, then a voltage comparison can preferably be used in that case before the actual monitoring, more preferably Each of the error tolerances (UAB, UBC, UCA) is, for example, 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 4% of the rated value of the respective mains voltage (Uae, Ube, Uce). , should be set to a somewhat lower value corresponding to 5%, 7% or 10%. If, for example, in each example of the second alternative, therefore, Ka = Ub/Ua and Kb = Uc/Ub and Kc = Ua/Uc are chosen for the setpoints, the voltage comparison before the actual monitoring can, if necessary, be It can be provided, or the voltage comparison can be performed before the actual monitoring, in which case preferably each of the error tolerances UAB, UBC, UCA is, for example, a respective mains voltage Uae, Ube, Uce ) is set to a rather high value corresponding to 2%, 3%, 4%, 5%, 7%, 10%, 15%, 20%, 25%, 30%, 40% or 50% of the rated value.

The at least one actual capacitance may be calculated as needed in any desired mode and manner, for example before, after or preferably simultaneously with calculating at least one of the other actual capacitances.

From here,

- error tolerances CA > 0, CB > 0, CC > 0 for capacitance comparison are determined; and

- If the capacitance comparison is

|C0a' - C0a| ≤ CA and |C0b' - C0b| ≤ CB and |C0c' - C0c| ≤ CC

A monitoring signal is generated indicating that the capacitor bushing is in a steady state.

Thus, after determining the error tolerance, the capacitance comparison is evaluated in a checking step, which is also referred to herein as a first evaluation or a first evaluation, and a monitoring signal according to this first evaluation is generated.

Each of these tolerances CA, CB, CC can be determined in any desired mode and manner as required, for example 0.001%, 0.002%, 0.003% of the respective upper capacitances C0a, C0b, C0c. , 0.004%, 0.005%, 0.007%, 0.01%, 0.012%, 0.015% or 0.02%. This mean value can be selected as desired as desired, for example as an arithmetic mean, geometric mean, harmonic mean or square mean. Each of these tolerance values and at least one other tolerance value may be the same as or different from each other.

From here,

- otherwise a monitoring signal is generated indicating that at least one capacitor bushing is not in normal condition.

Accordingly, this monitoring signal is generated in the case where the checked case does not exist as a result of the first evaluation.

From here,

- error tolerances CA > 0, CB > 0, CC > 0 for capacitance comparison are determined;

- Capacitance comparison result

C0a' - C0a < -CA and C0b' - C0b > CB and |C0c' - C0c| If ≤ CC,

a monitoring signal is generated indicating that at least the second capacitor bushing is not in a steady state;

- If the capacitance comparison result

C0b' - C0b < -CB and C0c' - C0c > CC and |C0a' - C0a| If ≤ CA,

a monitoring signal is generated indicating that at least the third capacitor bushing is not in a steady state;

- If the capacitance comparison result

C0c' - C0c < -CC and C0a' - C0a > CA and |C0b' - C0b| If ≤ CB,

A monitoring signal is generated indicating that at least the first capacitor bushing is not in a steady state.

Thus, after determining the error tolerance, the capacitance comparison is evaluated in four check steps, which is also referred to herein as a second evaluation or a second evaluation, and a monitoring signal according to the result of this second evaluation is generated. Each of these checking steps can be performed as needed in any desired mode and manner, for example before, after or preferably simultaneously with at least one other checking step.

Each of these tolerances CA, CB, CC is determined in any desired mode and manner as required, for example 0.001%, 0.002%, 0.003% of the respective upper capacitances C0a, C0b, C0c; It can be set to a value corresponding to 0.004%, 0.005%, 0.007%, 0.01%, 0.012%, 0.015%, or 0.02% or to the average value of the upper capacitances C0a, C0b, C0c. This mean value can be selected as desired as desired, for example as an arithmetic mean, geometric mean, harmonic mean or square mean. Each of these tolerance values and at least one other tolerance value may be the same as or different from each other. If the error tolerances CA, CB, CC have already been determined in any case, for example for the first evaluation or for the third evaluation described below, then it may be preferable that the error tolerances are also employed for this second evaluation. .

From here,

- otherwise a monitoring signal is generated indicating that at least two capacitor bushings are not in normal condition.

Accordingly, this monitoring signal is generated when the checked case does not exist as a result of the second evaluation.

From here,

- error tolerances CA > 0, CB > 0, CC > 0 for capacitance comparison are determined;

- If the capacitance comparison result,

C0a' - C0a > CA and C0b' - C0b < -CB and |C0c' - C0c| If ≤ CC,

A monitoring signal is generated indicating that the first and third capacitor bushings are not in a steady state and have the same fault;

- If the capacitance comparison result,

C0b' - C0b > CB and C0c' - C0c < -CC and |C0a' - C0a| If ≤ CA,

A monitoring signal is generated indicating that the second and first capacitor bushings are not in a steady state and have the same fault; and

- If the capacitance comparison result,

C0c' - C0c > CC and C0a' - C0a < -CA and |C0b' - C0b| If ≤ CB,

A monitoring signal is generated indicating that the third and second capacitor bushings are not in a steady state and have the same fault.

Thus, after determining the error tolerance, the capacitance comparison is evaluated in three check steps, also referred to herein as a third evaluation or a third evaluation, and a monitoring signal according to the result of this third evaluation is generated. Each of these checking steps can be performed as needed in any desired mode and manner, for example before, after or preferably simultaneously with at least one of the other checking steps.

Each of these error tolerances (CA, CB, CC) is performed in any desired mode and manner as required, for example 0.001%, 0.002%, 0.003% of the respective upper capacitance (C0a, C0b, C0c); It can be set to a value corresponding to 0.004%, 0.005%, 0.007%, 0.01%, 0.012%, 0.015%, or 0.02% or to the average value of the upper capacitances C0a, C0b, C0c. This mean value can be selected as desired as desired, for example as an arithmetic mean, geometric mean, harmonic mean or square mean. Each of these tolerance values and at least one other tolerance value may be the same as or different from each other. If error tolerances CA, CB, CC have already been determined in any case, for example for a first or second evaluation, then it may be preferable for error tolerances to be employed for this second evaluation as well.

According to a second aspect, the present invention provides a device for monitoring capacitor bushings for three-phase alternating current mains, each capacitor bushing comprising a conductor connected to one of the main lines of the alternating current mains, and said conductor A device comprising and/or suitable for and/or particularly operative to carry out one of the proposed methods, said device comprising:

- measuring device;

- a measuring adapter for each phase, said adapter connectable to a lining of a capacitor bushing belonging to each phase and connected with said measuring device for detecting a first electrical measuring variable; and

- propose a device having or comprising an evaluation device connected to the measuring device to communicate the first measuring variable to the evaluation device;

By combining the first measuring variable in the evaluation device, it becomes possible to implement central monitoring and to detect fluctuations in the mains voltage in all phases of the alternating current mains while monitoring all capacitor bushings. Reliable monitoring of the capacitor bushings is thus ensured.

This device proposed according to the second aspect enables continuous monitoring of the capacitor bushing.

Using the device proposed according to the second aspect makes it possible, for example, to carry out the proposed method.

The device proposed according to the second aspect can be configured in any desired mode and manner as required, for example at least one further measuring device and/or at least one further measuring adapter and/or at least one further evaluation It may include a device. It is possible, for example, to provide an individual measuring device and/or an individual evaluation device for each measuring adapter. Alternatively, the measuring device may be configured as a common measuring device for at least two adapters or for all measuring adapters.

The evaluation device can be configured as required in any desired mode and manner, for example as a common measuring device for at least two measuring devices or for all measuring devices. Alternatively or in addition to this, it may for example comprise an upper evaluation device and a measuring device belonging to each phase and a respective lower evaluation device for each phase connected with the upper evaluation device.

The main line may be configured in any desired mode and manner as required, for example as a high voltage line.

The device proposed according to the second aspect is preferably configured in such a way that it performs and/or is capable of performing one of the proposed methods.

The device proposed according to the second aspect additionally

- a voltage converter for each phase, said converter connectable with a main line belonging to each phase to detect and/or measure a second electrical measurement variable and communicate a second measurement parameter to said evaluation device It may have or include a voltage converter connected to.

By using a second measured variable detected by the voltage converter in the main line, fluctuations in time and/or fluctuations in time of the main voltage and/or the ratio of the mains voltage, such as for example instantaneous phenomena or asymmetry, are detected and/or it is possible to recognize and compare them with, for example, the first measured variable and/or its changes and/or fluctuations over time. It is thus ensured that fluctuations and/or fluctuations in the mains voltage are taken into account and evaluated and that the capacitor bushings are reliably monitored.

The evaluation device can be configured as required in any desired mode and manner, for example as a common measuring device for at least two measuring devices or for all measuring devices and/or for at least two voltage converters or for all voltage converters. . Alternatively or in addition to this, it comprises, for example, an upper evaluation device and a measuring device pertaining to each phase, a voltage converter pertaining to each phase and an individual evaluation device for each phase connected with the upper evaluation device. can do.

From here,

- Each voltage converter can be configured as a capacitive voltage converter or an inductive voltage converter or a resistive voltage converter.

Each voltage converter may be configured in any desired mode and manner as required and/or realized using other suitable principles. For example it may be configured inductively and/or capacitively and/or resistively and/or may include inductive and/or capacitive and/or resistive components and/or components. Preferably, it may comprise a capacitive voltage divider comprising two capacitors connected in series and two coils or windings connected as a transformer for inductive electrical isolation.

From here,

- the measuring device or at least one of the measuring devices comprises at least one measuring capacitor.

The capacitance of at least one of the measuring capacitors is preferably a multiple of the capacitance of the respective external capacitor.

The capacitance of the measuring capacitors usually has a value between 1 and 5 μF, but if desired they may have other values, for example between 0.1 μF and 50 μF or between 0.2 μF and 20 μF or between 0.5 μF and 10 μF It can have values between

The capacitance of the measuring capacitor can be selected in any desired mode and manner as required. Thus, for example, if a measuring adapter in each phase is connected with an individual measuring capacitor associated only with that adapter and these three measuring capacitors are integrated in a common measuring device or distributed to the three individual measuring devices associated with the measuring adapter. , the capacitances of these three measuring capacitors can be the same value, or two of these capacitors can be the same and have a different value than the third capacitance, or all three capacitances can be different values. These three capacitances are, for example, 1:2:3, 1:2:4, 1:2:5, 1:3:5, 1:3:7, 1:3:9, 1:4: It can be in a ratio of 7 or 1:4:9.

From here,

- The first measurement variable is the voltage respectively applied to the lower voltage capacitor of each phase.

Each lower voltage capacitor can be configured in any desired mode and manner as required, for example between 0.1 μF and 50 μF or between 0.2 μF and 20 μF or between 0.5 μF and 10 μF or between 1 μF and 5 μF It can have a capacitance between -referred to herein as the lower capacitance. Alternatively or additionally, each of these lower capacitances and at least one of the other lower capacitances may have the same or different values. For example, the lower capacitances are 1:2:3, 1:2:4, 1:2:5, 1:3:5, 1:3:7, 1:3:9, 1:4:7 or It may be a ratio of 1:4:9.

From here,

- The second measurement variable is the voltage applied between each main line and the ground potential.

This voltage is also referred to herein as the main voltage.

From here,

- The evaluation device,

- calculate or be configured to calculate the actual capacitance for each capacitor bushing, wherein the actual capacitance is at each measured voltage and lower capacitance of each capacitor bushing and the measured voltage, lower capacitance and upper capacitance of one of the remaining capacitor bushings; depend on

From here,

- The evaluation device,

- is configured to compare or compare each upper capacitance with the respective actual capacitance for each capacitor bushing;

According to a third aspect the invention proposes a device for monitoring a capacitor bushing for a three-phase alternating current main, each capacitor bushing having a conductor connected to one of the main lines of the alternating current main and a conductive lining surrounding the conductor comprising, such a device being particularly configured as one of the devices proposed according to the second aspect,

- means configured to detect the measured voltage U1a, U1b, U1c appearing between the respective lining and the ground potential in each capacitor bushing;

- for each capacitor bushing the respective measured voltages U1a, U1b, U1c and lower capacitances C1a, C1b, C1c of each capacitor bushing and the lower capacitances C1b, C1c, C1a of one of the remaining capacitor bushings; ) and means for performing and/or suitable for calculating the actual capacitances C0a', C0b', C0c' depending on the upper capacitances C0b, C0c, C0a;

- means configured and/or performing and/or suitable for comparing the respective upper capacitances C0a, C0b, C0c with the respective actual capacitances C0a', C0b', C0c' for each capacitor bushing ; and

- having or comprising means configured and/or performing and/or suitable for generating a monitoring signal according to a result of the capacitance comparison;

By combining the measured voltages in the means for detecting the measured voltages, it is possible to realize central monitoring and thus to detect fluctuations in the mains voltages in all phases of the alternating current mains when all capacitor bushings are alternating current mains. becomes Reliable monitoring of the capacitor bushings is thus ensured.

This device proposed according to the third aspect is able to compare the upper capacitance of the capacitor bushing and its actual capacitance in operation with each other, which is referred to herein as capacitance comparison. If the actual capacitance changes, it can be determined that the corresponding capacitor bushing is damaged.

The device proposed according to the third aspect enables continuous monitoring of the capacitor bushing.

It is possible, for example, to perform one of the proposed methods using the proposed device according to the third aspect.

The device proposed according to the third aspect may be configured as needed in any desired mode and manner, for example as one of the devices proposed according to the second aspect.

The means for detecting the measured voltage may be configured in any desired mode and manner as required and may be connected, for example, with means for calculating an actual capacitance and/or means for comparing capacitance and/or measuring device and/or for each phase a measuring adapter which may be connected with the lining of the capacitor bushing belonging to each phase and which may be connected with the measuring device for detecting and/or measuring the respective measured voltage.

The means for calculating the actual capacitance may be configured in any desired mode and manner as required and may be connected, for example, with means for detecting a measured voltage and/or means for comparing capacitance, and/or It may include an evaluation device coupled to the measuring device for communicating the measured voltage to the evaluation device.

For example, an individual measuring device and/or a separate evaluation device may be provided for each measuring adapter. Alternatively, the measuring device may be configured as a common measuring device for at least two adapters or for all measuring adapters.

The means for capacitance comparison can be configured in any desired mode and manner as required and can be connected, for example, to means for detecting a measured voltage and/or means for calculating an actual capacitance and/or an evaluation device. and may comprise means for calculating the actual capacitance and/or individual evaluation devices and/or may be combined or combined with means for calculating the actual capacitance to form a common means or for calculating the actual capacitance may be implemented by means or included within means for calculating the actual capacitance or may comprise means for calculating the actual capacitance.

The means for generating the monitoring signal can be configured according to need in any desired mode and manner, for example connected with the means for capacitance comparison and/or at least one acoustic signal transmitter and/or at least one optical It may comprise a signal transmitter and/or at least one electronic signal transmitter and/or may be included in the means for calculating the actual capacitance and/or in the means for comparing the capacitances.

The device proposed according to the third aspect is

- means configured and/or operated and/or suitable for measuring the mains voltages Ua, Ub, Uc for each phase;

- means configured and/or operated and/or suitable for comparing the mains voltages with each other; and

- if, as a result of voltage comparison, the mains voltages differ from each other by less than or equal to a predetermined amount (UAB, UBC, UCA), configured and/or operated for and/or causing the calculation of actual capacitance, comparison of capacitance and generation of monitoring signals; It may have or include means suitable for carrying out, carrying out or initiating.

By using the mains voltage, for example, changes in time and/or fluctuations in time of the mains voltage such as instantaneous phenomena or asymmetry can be detected and/or recognized and, for example, they can be detected and/or recognized by the mains voltage and/or its time It becomes possible to compare changes and/or fluctuations according to It is thus ensured that fluctuations and/or fluctuations in the mains voltage are taken into account and evaluated and that the capacitor bushings are reliably monitored.

This comparison of the mains voltage is also referred to herein as a voltage comparison, whereby it is possible to determine the moment when the actual monitoring - ie the calculation of the actual capacitance, the comparison of the capacitances and the generation of the monitoring signal - is particularly advantageous and desirable, since This is because the operation is not made difficult, hampered or even impossible to perform by the mains voltages differing from each other by more than a predetermined amount. Thus, a better statement of the condition of the capacitor bushing can be made irrespective of fluctuations in the mains voltage and tolerance for measurement errors during the detection of the measured voltage.

By taking the mains voltage into account, it becomes possible, for example, to detect a change over time in the voltage ratio (also called asymmetry), thus at least partially compensating for the corresponding deviation of the measured voltage measured at the capacitor bushing. This enables reliable monitoring of the capacitor bushings taking into account and evaluating variations and disturbances in the mains voltage.

Means for calculating the actual capacitance, comparing the capacitances and allowing to generate a monitoring signal are also referred to herein for short as means for causing.

The means for detecting the mains voltage may be configured in any desired mode and manner as required, for example connected to the means for comparing voltages and/or detecting the respective measured voltage for each phase and/or a voltage converter that can be connected to a main line belonging to each phase for measurement. For example they may additionally be connected with means for calculating the actual capacitance and/or means for comparing the capacitances.

The means for voltage comparison can be configured according to need in any desired mode and manner, for example connected with means for detecting the mains voltage and/or with triggering means, and/or the evaluation device can measure the actual capacitance. It may comprise means for calculating and/or the evaluation device may comprise means for capacitance comparison and/or means for detecting the mains voltage and/or a respective evaluation device connected to the voltage converter. For example they may additionally be connected with means for calculating the actual capacitance and/or means for comparing the capacitances. Alternatively or in addition to this, they may be combined or combined with means for calculating the actual capacitance and/or means for comparing the capacitance and/or causing means to form a common means, or means for calculating the actual capacitance and and/or may be implemented by means and/or means for causing capacitance comparison, or may be included within the means for calculating actual capacitance and/or means for comparing capacitance and/or means for causing, or calculating the actual capacitance means for and/or means for capacitance comparison and/or means for causing.

The inducing means may be configured in any desired mode and manner as required, for example means for voltage comparison and/or means for calculating actual capacitance and/or means for capacitance comparison and/or monitoring signals. may be connected with means for generating, and/or the evaluation device may comprise means for voltage comparison, and/or the evaluation device may comprise means for calculating an actual capacitance, and/or the evaluation device is an individual evaluation device connected with means for comparing capacitance and/or means for comparing voltage and/or means for calculating actual capacitance and/or means for comparing capacitance and/or means for generating a monitoring signal may include Alternatively or additionally, they may be combined or combined with means for voltage comparison and/or means for calculating actual capacitance and/or means for capacitance comparison to form common means, or means for voltage comparison and and/or may be implemented by means for calculating the actual capacitance and/or means for comparing the capacitances or may be included in the means for comparing the voltages and/or the means for calculating the actual capacitance and/or the means for comparing the capacitances or means for voltage comparison and/or means for calculating actual capacitance and/or means for capacitance comparison.

From here,

- each of the proposed devices is configured and/or operative and/or suitable for carrying out and/or capable of carrying out one of the proposed methods;

Each of the methods proposed according to the first aspect and each of the devices proposed according to the second or third aspect have a relatively large measurement error tolerance and/or measurement accuracy and preferably have the same error tolerance class and/or accuracy It belongs to a class and in particular allows the use of identical voltage converters.

Descriptions and descriptions relating to one of the aspects of the invention, in particular to individual features of that aspect, apply correspondingly to the other aspect of the invention as well.

Aspects of an embodiment of the present invention are described in more detail below by way of illustration on the basis of the drawings. However, the individual features evident from these are not limited to individual forms of the embodiments, but may be associated with and/or combined with individual features further described above and/or individual features of other forms of other embodiments. The details of the drawings are to be understood in an illustrative sense only and not in a limiting sense. Reference numerals included in the claims do not in any case limit the protection scope of the present invention, but relate only to the forms of the embodiments shown in the drawings. From the drawing:
1 shows the form of an embodiment of a device for monitoring capacitor bushings for three-phase alternating current mains;
2 shows a part of the device of FIG. 1 ;
3 shows an equivalent circuit consisting of a lower voltage capacitor and an upper voltage capacitor; and
4 shows a flow diagram in the form of one embodiment of a method of monitoring a capacitor bushing for a three-phase alternating current main;

A device 1 for capacitor bushings 2a, 2b, 2c for three-phase alternating current mains is schematically shown in FIG. 1 . In this form of embodiment, the capacitor bushings 2a, 2b, 2c are not shown in the figure and here they belong to a transformer, for example a high voltage transformer. Capacitor bushings 2a, 2b, 2c of this kind are used, for example, at high voltages ranging from a few kilovolts to several thousand kilovolts. The alternating current main is here for example a high voltage main. Each of the three capacitor bushings 2a, 2b, 2c is associated with one of the three phases Pa, Pb, Pc of the alternating current mains and is connected to the respective main lines 5a, 5b, 5c of the alternating current mains a conductor 4 which is formed, and several conductive linings sealing the conductor 4 with several layers or plies, of which only the outermost lining 3 is shown.

The device 1, together with the evaluation device 8, is configured to detect the device 7 for each phase Pa, Pb, Pc and a first electrical measurement variable for each phase Pa, Pb, Pc. It comprises a measuring adapter 6 connected to the respective measuring device 7 and the lining 3 of the capacitor bushings 2a , 2b , 2c belonging to the respective phase. This first measurement variable appears here, respectively, on the lower voltage capacitors KU1, KU2, KU3 (further described and shown in Fig. 3) of the respective phases Pa, Pb, Pc, and here the measured voltage ( These voltages are also called U1a, U1b, U1c). The evaluation device 8 is connected to each measuring device 7 to communicate the measured voltages U1a, U1b, U1c to the evaluation device 8 , and thus a common evaluation device 8 for all measuring devices 7 . ) to form

In this form of embodiment the device 1 measures each of the main lines 5a, 5b to measure a second electrical measurement variable for each phase Pa, Pb, Pc for each phase Pa, Pb, Pc. , 5c) further comprising voltage converters 9a, 9b, 9c. These second measurement variables are voltages that appear in the respective main lines 5a, 5b, 5c and the ground potential 13, respectively, in this specification, and are also referred to herein as the main voltages Ua, Ub, Uc. The evaluation device 8 is connected with the respective voltage converters 9a , 9b , 9c to communicate the main voltages Ua , Ub , Uc to the evaluation device 8 , and thus all voltage converters 9a , 9b , 9c to form a common evaluation device 8 for

Via device 1, in the evaluation device 8 under consideration, the main voltages Ua, Ub, Uc appearing on the main lines 5a, 5b, 5c when monitoring the capacitor bushings 2a, 2b, 2c Asymmetry and/or fluctuations can be detected.

The part associated with the first phase Pa of the device 1 is shown in detail in FIG. 2 . The second part of the device 1 associated with the second phase Pb and the third part of the device 1 associated with the third phase Pc correspond in a similar way to this first part, and thus to the first part The descriptions and descriptions of these apply in a similar manner to correspond to these two other parts as well.

The first capacitor bushing 2a associated with the first phase Pa comprises an insulating body 11 , through which a conductor 4 is guided. It contacts at its upper end the main line 5a associated with its capacitor bushing 2a and at its lower end a winding (not shown) of a high voltage transformer. Only the outermost lining 3 is shown here in the insulating body 11 and a conductive lining, which from an electrical point of view forms a series circuit of capacitors, is embedded. This series circuit includes a capacitor each formed by two adjacent linings, and a capacitor formed by an innermost lining (not shown in the figure) and a conductor 4 . This series circuit of capacitors between the outermost lining 3 and the conductor 4, as an equivalent circuit for each capacitor bushing 2a, 2b, 2c, produces a capacitance called the upper capacitance C0a, C0b, C0c. The branches form corresponding upper voltage capacitors KO1, KO2, KO3.

A conductive flange 12 at earth potential or earth potential 13 is arranged on the capacitor bushing 2a. This flange 12 fastens and/or secures the capacitor bushing 2a. Outermost lining 3 is an equivalent circuit for each capacitor bushing 2a, 2b, 2c, together with flange 12 and ground potential 13, corresponding external capacitors having capacitances CA1, CA2, CA3 KA1, KA2, and KA3 are formed.

The measuring adapter 6 passes through the insulating body 11 and forms a conductive connection with the outermost lining 3 . It is electrically conductively connected by each measuring device 7 to the evaluation device 8 so as to be able to detect the measured voltage U1a and communicate it to the evaluation device 8 . Each measuring device 7 in this form of embodiment comprises measuring capacitors KM1 , KM2 , KM3 having capacitances CM1 , CM2 , CM3 , which are connected with a ground potential 13 . If necessary, the measuring device includes a radio path (not shown) connected in parallel with the respective measuring capacitors KM1, KM2, KM3 and/or overvoltage protection means 7 connected in parallel with the respective measuring capacitors KM1, KM2, KM3. ') is further included.

The evaluation device 8 is conductively connected to the main line 5a via a voltage converter 9a. The voltage Ua between the main line 5a and the ground potential 13 is detected by this connection. In this form of embodiment, the voltage converter 9a is configured as a capacitive voltage converter, two capacitors K1, K2 connected in series and two coils or windings W1, W2 connected as a transformer for inductive electrical isolation. ) is included.

Such a device 1 may be suitable for and/or configured in such a way as to carry out a method for monitoring a capacitor bushing for a three-phase alternating current main. One form of embodiment of this kind of method is further described below.

An equivalent circuit consisting of each lower voltage capacitor KU1 and each upper voltage capacitor KO1 is schematically illustrated in FIG. 3 for the first phase Pa. A parallel circuit comprising each measuring capacitor KM1 and an external capacitor KA1 forms a lower voltage capacitor KU1 having a lower capacitance C1. Therefore, this lower capacitance C1 can be easily calculated from the capacitance CM1 of the measuring capacitor KM1 and the capacitance CA1 of the external capacitor KA1 by a known formula for a series circuit of capacitors. If necessary, the parallel circuit can comprise the entire individual measuring device 7 and/or additionally the evaluation device 8 instead of the measuring capacitor KM1, in which case the capacitance CA1 is equal to the capacitance of the evaluation device 8 ( It has to be calculated from the impedance of the measuring device 7 , which depends on CM1), the capacitance CA1 and the impedance.

As mentioned above, the measured voltage U1a appears on the lower voltage capacitor KU1 and is measured at the connecting line or junction between the lower voltage capacitor KU1 and the upper voltage capacitor KO1, called the ground potential 13 . is called The main voltage Ua falls while passing through the series circuit of the upper voltage capacitor KO1 and the lower voltage capacitor KU1.

A flow diagram of one form of an embodiment of a method for monitoring a three-phase alternating current mains capacitor bushings 2a, 2b, 2c is schematically shown in FIG. 4 . This method can be performed, for example, by and/or with the aid of the device 1 of FIG. 1 .

This method in this form of embodiment comprises the device 1 and the following steps described with reference to FIGS. 1 and 2 :

Step 101: Start of the method

Step 102 : Upper capacitance C0a, C0b, C0c and lower capacitance C1a, C1b, C1c are determined for each capacitor bushing 2a, 2b, 2c. These are registered as fixed values.

Step 103 : The measured voltages U1a, U1b, U1c are detected at the respective capacitor bushings 2a, 2b, 2c. Mains voltages Ua, Ub, Uc are detected for each phase Pa, Pb, Pc.

Step 104 : The main voltages (Ua, Ub, Uc) are calculated again as RMS values (Uae, Ube, Uce) and compared with each other.

In this form of embodiment, error tolerances UAB > 0, UBC > 0, UCA > 0 are determined for voltage comparison,

|Uae - Ube| ≤ UAB and |Ube - Uce| ≤ UBC and |Uce - Uae| Voltage comparison is performed in such a way that it checks whether ≤ UCA.

If so, this means that as a result of the voltage comparison, the main voltages Ua, Ub, Uc do not differ from each other by a value greater than the predetermined amount UAB, UBC, UCA. In this case, step 106 is performed.

Otherwise, this means that as a result of the voltage comparison, the main voltages Ua, Ub, and Uc are different from each other by a value greater than a predetermined amount (UAB, UBC, UCA). In this case, step 105 is performed.

Step 105 : A warning signal is generated indicating a short circuit in the current mains and/or too strong or excessive asymmetry of the mains voltages Ua, Ub, Uc. Subsequently, the flow moves to step 103 .

Step 106 : Actual capacitances C0a', C0b', C0c' are calculated for each capacitor bushing 2a, 2b, 2c, where the actual capacitance is calculated for each of the measured voltages U1a, U1b, U1c, respectively The measured voltages U1b, U1c, U1a of one of the remaining capacitor bushings 2b, 2c, 2a, the lower capacitances C1b, C1c, C1a and the upper capacitance C0b, C0c, C0a).

In this form of embodiment

The actual capacitances C0a', C0b', C0c' of the capacitor bushings 2a, 2b, 2c are calculated by the formula:

where Ka is a fixed value such that Ka = Ub/Ua;

where Kb is a correction value such that Kb = 1 or Kb = Uc/Ub; and

Here, Kc is a fixed value where Kc = Ua/Uc.

Step 107 : For each capacitor bushing 2a, 2b, 2c, the respective upper capacitance C0a, C0b, C0c is compared with the respective actual capacitance C0a', C0b', C0c'.

In this form of the embodiment, error tolerances CA > 0, CB > 0, CC > 0 for the capacitance comparison are determined, and the capacitance comparison is

|C0a' - C0a| ≤ -CA and |C0b' - C0b| ≤ CB and |C0c' - C0c| It is performed in such a way that it is first checked whether ≤ CC.

If so, step 108 is performed. If not, step 109 is performed.

Step 108 : A monitoring signal is generated indicating that the capacitor bushings 2a, 2b, 2c are in a steady state. Subsequently, the flow moves to step 103 .

Step 109 : additional capacitance comparison

C0a' - C0a < -CA and C0b' - C0b > CB and |C0c' - C0c| It is performed in a way that checks whether ≤ CC.

If so, step 110 is performed. If not, step 111 is performed.

Step 110 : A monitoring signal is generated indicating that at least the second capacitor bushing 2b is not in a steady state. Then, it moves to step 122.

Step 111 : additional capacitance comparison

C0b' - C0b < -CB and C0c' - C0c > CC and |C0a' - C0a| It is performed in such a way that it checks whether ≤ CA.

If so, step 112 is performed. If not, step 113 is performed.

Step 112 : A monitoring signal is generated indicating that at least the third capacitor bushing 2c is not in a steady state. Subsequently, the flow moves to step 122 .

Step 113 : additional capacitance comparison

C0c' - C0c < -CC and C0a' - C0a > CA and |C0b' - C0b| It is performed in such a way that it checks whether ≤ CB.

If so, step 114 is performed. If not, step 115 is performed.

Step 114 : A monitoring signal is generated indicating that at least the first capacitor bushing 2a is not in a steady state. Now go to step 122 .

Step 115 : A monitoring signal is generated indicating that the at least two capacitor bushings are not in a steady state.

Step 116 : Additional capacitance comparison is performed

C0a' - C0a > -CA and C0b' - C0b < -CB and |C0c' - C0c| It is performed in a way that checks whether ≤ CC.

If so, step 117 is performed. If not, step 118 is performed.

Step 117 : A monitoring signal is generated indicating that the first and third capacitor bushings 2a, 2c are not in their steady state and have the same fault. Now go to step 122 .

Step 118 : Additional capacitance comparison is performed

C0b' - C0b > CB and C0c' - C0c < -CC and |C0a' - C0a| It is performed in such a way that it checks whether ≤ CA.

If so, step 119 is performed. If not, step 120 is performed.

Step 119 : A monitoring signal is generated indicating that the second and first capacitor bushings 2b, 2a are not in a steady state and have the same fault. Now go to step 122 .

Step 120 : Additional capacitance comparison is performed

C0c' - C0c > CC and C0a' - C0a < -CA and |C0b' - C0b| It is performed in such a way that it checks whether ≤ CB.

If so, step 121 is performed. If not, step 122 is performed.

Step 121 : A monitoring signal is generated indicating that the third and second capacitor bushings 2c, 2b are not in a steady state and have the same fault. Now go to step 122 .

Step 122 : A monitoring signal is generated indicating that the at least two capacitor bushings are not in a steady state and have other faults. The method is now over, or if necessary, go to step 103 .

Step 102 can be performed, for example, by the evaluation device 8 .

Step 103 can, for example, be carried out by means of a measuring adapter 6 , a measuring device 7 and an evaluation device 8 on the one hand, which now respectively in the respective capacitor bushings 2a, 2b, 2c Forming means configured in such a way as to detect the measured voltages U1a, Ulb, U1c appearing between the lining 3 and the ground potential 13, on the other hand the voltage converters 9a, 9b, 9c and evaluation It can be carried out by the device 8 , which together form means which are configured in such a way as to detect the mains voltages Ua, Ub, Uc of the respective phases Pa, Pb, Pc.

Steps 104 and 105 can, for example, be performed by the evaluation device 8 , thus forming means that are configured in such a way as to compare the mains voltages Ua, Ub, Uc with each other.

Step 106 can be performed, for example, by the evaluation device 8 , which accordingly for each capacitor bushing 2a each measured voltage U1a of each capacitor bushing 2a, 2b, 2c, U1b, U1c), the lower capacitances C1a, C1b, C1c and the measured voltages U1b, U1c, U1a of one of the remaining capacitor bushings 2b, 2c, 2a, the lower capacitances C1b, C1c, C1a and form means, which are arranged in such a way as to calculate the actual capacitances C0a', C0b', C0c' depending on the upper capacitances C0b, C0c, C0a.

Steps 107 , 109 , 111 , 113 , 116 , 118 and 120 can be performed, for example, by the evaluation device 8 , so that for each capacitor bushing 2a , 2b , 2c the respective upper capacitance (C0a, C0b, C0c) is formed in such a way that it is compared with the respective actual capacitances C0a', C0b', C0c'.

Steps 108 , 110 , 112 , 114 , 115 , 117 , 119 , 121 and 122 can, for example, be performed by the evaluation device 8 , so that they are configured in such a way as to generate a monitoring signal according to the result of the capacitance comparison. form the means to become

Reference number list

1 device

2a, 2b, 2c capacitor bushings

3 lining

4 conductor

5a, 5b, 5c main line

6 measuring adapter

7 Measuring device

7' Overvoltage protection means

8 evaluation device

9a, 9b, 9c voltage converter

11 insulated body

12 flange

13 ground potential

K1, K2 capacitors

W1, W2 winding

Pa, Pb, Pc 1st, 2nd, 3rd phase

Ua, Ub, Uc main voltage

Uae, Ube, Uce RMS of main voltage

SP1, SP2, SP3 voltage divider

KO1, KO2, KO3 first, second, third upper voltage capacitors

KU1, KU2, KU3 first, second and third lower voltage capacitors

KA1, KA2, KA3 first, second and third external capacitors

KM1, KM2, KM3 1st, 2nd and 3rd measuring capacitors

Upper capacitance of C0a, C0b, C0c KO1, KO2, KO3

Actual capacitance of C0a', C0b', C0c' KO1, KO2, KO3

Bottom capacitance of C1a, C1b, C1c KU1, KU2, KU3

CA1, CA2, CA3 Capacitance of KA1, KA2, KA3

CM1, CM2, CM3 Capacitance of KM1, KM2, KM3

Measured voltage at U1a, U1b, U1c 6

Ka, Kb, Kc Corrections

Tolerance of CA, CB and CC capacitances

Error tolerance for UAB, UBC, UCA voltage comparison

Claims (25)

A method of monitoring capacitor bushings (2a, 2b, 2c) for three-phase alternating current mains, wherein each capacitor bushing (2a, 2b, 2c) has a main line (5a, 5b, 5c) of alternating current mains ) comprising a conductor (4) connected to one of the
- determining the upper capacitances C0a, C0b, C0c and the lower capacitances C1a, C1b, C1c for each capacitor bushing 2a, 2b, 2c;
- detecting in the respective capacitor bushings (2a, 2b, 2c) the measured voltages (U1a, U1b, U1c) appearing between the respective conductive linings (3) and the ground potential (13);
- calculating the actual capacitances C0a', C0b', C0c' for each of the capacitor bushings 2a, 2b, 2c, wherein the actual capacitances correspond to the respective measured voltages U1a, U1b, U1c, respectively to the lower capacitances C1a, C1b, C1c and the measured voltages U1b, U1c, U1a of one of the remaining capacitor bushings 2b, 2c, 2a, the lower capacitances C1b, C1c, C1a, and the upper capacitances calculation step, depending on C0b, C0c, C0a);
- comparing the respective upper capacitances C0a, C0b, C0c with the respective actual capacitances C0a', C0b', C0c' for each capacitor bushing 2a, 2b, 2c; and
- a method for monitoring a capacitor bushing comprising the step of generating a monitoring signal according to a result of the capacitance comparison. The method of claim 1,
- the mains voltages Ua, Ub, Uc appearing on the respective main lines 5a, 5b, 5c are detected for the respective phases Pa, Pb, Pc;
- the mains voltages Ua, Ub, Uc are compared with each other; and
- as a result of comparing the main voltages, if the main voltages Ua, Ub, Uc differ from each other by less than a predetermined amount UAB, UBC, UCA, the calculation of the actual capacitances C0a', C0b', C0c', the A method for monitoring a capacitor bushing, wherein a comparison of the upper capacitances (C0a, C0b, C0c) with the actual capacitances (C0a', C0b', C0c') and generation of the monitoring signal takes place. 3. The method of claim 2,
- at least one of the rms values (Uae, Ube, Uce), peak values and amplitudes of the main voltages (Ua, Ub, Uc) is used for comparison of the main voltages, a capacitor bushing monitoring method. 4. The method of claim 3,
- error tolerances for the comparison of the mains voltages UAB > 0, UBC > 0, UCA > 0 are determined;
- Comparison of main voltages is |Uae - Ube| ≤ UAB and |Ube - Uce| ≤ UBC and |Uce - Uae| Capacitor bushing monitoring method, performed in such a way as to check that ≤ UCA. 5. The method according to any one of claims 1 to 4,
- the actual capacitance C0a' of the first capacitor bushing 2a is

is calculated according to
Ka is a correction value such that Ka = 1 or Ka = Ub/Ua;
- the actual capacitance C0b' of the second capacitor bushing 2b is

is calculated according to
Kb is Kb = 1 or Kb = Uc/Ub;
- the actual capacitance C0c' of the third capacitor bushing 2c is

is calculated according to
A method for monitoring capacitor bushings, wherein Kc is Kc = 1 or a constant value where Kc = Ua/Uc. 5. The method according to any one of claims 1 to 4,
- an error tolerance for the capacitance comparison CA > 0, CB > 0, CC > 0 is determined;
- Capacitance comparison result
|C0a' - C0a| ≤ CA and |C0b' - C0b| ≤ CB and |C0c' - C0c| If ≤ CC,
and a monitoring signal is generated indicating that the capacitor bushings (2a, 2b, 2c) are in an orderly state. 7. The method of claim 6,
- Capacitance comparison result
|C0a' - C0a| ≤ CA and |C0b' - C0b| ≤ CB and |C0c' - C0c| If ≤ CC,
and a monitoring signal is generated indicating that the at least one capacitor bushing is not in a steady state. 5. The method according to any one of claims 1 to 4,
- error tolerances CA > 0, CB > 0, CC > 0 for the capacitance comparison are determined;
- Capacitance comparison result
C0a' - C0a < -CA and C0b' - C0b > CB and |C0c' - C0c| If ≤ CC
a monitoring signal is generated indicating that at least the second capacitor bushing 2b is not in a steady state;
- Capacitance comparison result
C0a' - C0a < -CA and C0b' - C0b > CB and |C0c' - C0c| If ≤ CC, the capacitance comparison result is
C0b' - C0b < -CB and C0c' - C0c > CC and |C0a' - C0a| If ≤ CA
a monitoring signal is generated indicating that at least the third capacitor bushing 2c is not in a steady state;
- Capacitance comparison result
C0b' - C0b < -CB and C0c' - C0c > CC and |C0a' - C0a| If ≤ CA, the capacitance comparison result is
C0c' - C0c < -CC and C0a' - C0a > CA and |C0b' - C0b| If ≤ CB
A monitoring signal is generated indicating that at least the first capacitor bushing (2a) is not in a steady state. 9. The method of claim 8,
- Capacitance comparison result
C0c' - C0c < -CC and C0a' - C0a > CA and |C0b' - C0b| If ≤ CB,
A method of monitoring a capacitor bushing, wherein a monitoring signal is generated indicating that at least two capacitor bushings are not in a steady state. 5. The method according to any one of claims 1 to 4,
- error tolerances for capacitance comparison CA > 0, CB > 0, CC > 0 are determined,
The capacitance comparison result is
C0a' - C0a > CA and C0b' - C0b < -CB and |C0c' - C0c| If ≤ CC
a monitoring signal is generated indicating that the first and third capacitor bushings 2a, 2c are not in a steady state and have the same fault;
- Capacitance comparison result
C0a' - C0a > CA and C0b' - C0b < -CB and |C0c' - C0c| If ≤ CC, the capacitance comparison result is
C0b' - C0b > CB and C0c' - C0c < -CC and |C0a' - C0a| If ≤ CA
a monitoring signal is generated indicating that the second and first capacitor bushings 2b, 2a are not in a steady state and have the same fault;
- Capacitance comparison result
C0b' - C0b > CB and C0c' - C0c < -CC and |C0a' - C0a| If ≤ CA, the capacitance comparison result is
C0c' - C0c > CC and C0a' - C0a < -CA and |C0b' - C0b| If ≤ CB
and a monitoring signal is generated indicating that the third and second capacitor bushings (2c, 2b) are not in a steady state and have the same fault. A device (1) for monitoring a capacitor bushing (2a, 2b, 2c) for a three-phase alternating current main, wherein each of the capacitor bushings (2a, 2b, 2c) is one of the main lines (5a, 5b, 5c) of the alternating current main a conductor (4) connected to one, and a conductive lining (3) surrounding the conductor (4), the device comprising:
- measuring device 7 ;
- a measuring adapter (6) for each phase (Pa, Pb, Pc), which can be connected to the conductive lining (3) of the capacitor bushings (2a, 2b, 2c) belonging to the respective phase and to the first a measuring adapter, connected with the measuring device (7) for detecting an electrical measuring variable; and
- a monitoring device (1) comprising an evaluation device (8) connected to the measuring device (7) to communicate a first electrical measurement variable to the evaluation device (8). 12. The method of claim 11,
- a voltage converter (9a, 9b, 9c) for each phase, which voltage converter can be connected with the main line (5a, 5b, 5c) belonging to the respective phase for detecting a second electrical measurement variable and a second electrical Monitoring device (1), further comprising a voltage converter, connected with the evaluation device (8) to communicate a measurement variable to the evaluation device (8). 13. The method of claim 12,
- monitoring device 1 , wherein each voltage converter 9a, 9b, 9c is configured as a capacitive voltage converter or an inductive voltage converter or a resistive voltage converter. 14. The method of claim 13,
- monitoring device (1), wherein said measuring device (7) comprises at least one measuring capacitor (KM1, KM2, KM3). 15. The method of claim 14,
- said measuring device 7 comprises three measuring capacitors KM1, KM2, KM3;
- a measuring adapter in each phase is connected with an associated measuring capacitor;
- the monitoring device 1 , the capacitances of these three measuring capacitors being different. 16. The method of claim 15,
- 3 capacitances are 1:2:3, 1:2:4, 1:2:5, 1:3:5, 1:3:7, 1:3:9, 1:4:7 or 1:4 A monitoring device (1), in a ratio of :9. 17. The method according to any one of claims 11 to 16,
- the monitoring device 1 , wherein the first electrical measurement variable is the measured voltage U1a, U1b, U1c respectively appearing on the lower voltage capacitors KU1 , KU2 , KU3 of the corresponding phase. 18. The method of claim 17,
- monitoring device 1 , the second electrical measurement variable being the voltages Ua, Ub, Uc appearing respectively between the corresponding main lines 5a, 5b, 5c and the ground potential 13 respectively. 19. The method of claim 18,
- the evaluation device (8),
- calculate the actual capacitances C0a', C0b', C0c' for each capacitor bushing 2a, 2b, 2c, said actual capacitance being the measured capacitance of each capacitor bushing 2a, 2b, 2c voltages U1a, U1b, U1c and the lower capacitances C1a, C1b, C1c and the measured voltage U1b, U1c, U1a of one of the remaining capacitor bushings 2b, 2c, 2a, the lower capacitance C1b, Monitoring device 1 , configured to depend on C1c, C1a) and upper capacitances C0b, C0c, C0a. 20. The method of claim 19,
- the evaluation device (8),
- a monitoring device, configured to be able to compare the respective upper capacitances C0a, C0b, C0c with the respective actual capacitances C0a', C0b', C0c' for the respective capacitor bushings 2a, 2b, 2c ( One). 17. The method according to any one of claims 11 to 16,
A monitoring device ( 1 ), configured to perform a method according to claim 1 . A device (1) for monitoring a capacitor bushing (2a, 2b, 2c) for a three-phase alternating current main, wherein each of the capacitor bushings (2a, 2b, 2c) is one of the main lines (5a, 5b, 5c) of the alternating current main a conductor (4) connected to one, and a conductive lining (3) surrounding the conductor (4), said device comprising:
- means configured to detect the measured voltages U1a, U1b, U1c appearing between the respective conductive lining 3 and the ground potential 13 in the respective capacitor bushings 2a, 2b, 2c;
- for each capacitor bushing 2a, 2b, 2c, to the respective measured voltages U1a, U1b, U1c and the lower capacitances C1a, C1b, C1c of the respective capacitor bushings 2a, 2b, 2c and the actual capacitance dependent on the measured voltages U1b, U1c, U1a, the lower capacitances C1b, C1c, C1a and the upper capacitances C0b, C0c, C0a of one of the remaining capacitor bushings 2b, 2c, 2a. means configured to calculate (C0a', C0b', C0c');
- means configured to compare the respective upper capacitances C0a, C0b, C0c with the respective actual capacitances C0a', C0b', C0c' for the respective capacitor bushings 2a, 2b, 2c; and
- a monitoring device (1) comprising means configured to generate a monitoring signal according to a result of the capacitance comparison. 23. The method of claim 22,
- means configured to detect the main voltages Ua, Ub, Uc of the respective phases Pa, Pb, Pc;
- means configured to compare the mains voltages Ua, Ub, Uc with each other; and
- As a result of comparing the main voltages, if the main voltages (Ua, Ub, Uc) differ by less than a predetermined amount (UAB, UBC, UCA) from each other, the calculation of the actual capacitances (C0a', C0b', C0c'), the upper capacitance ( Monitoring device ( 1 ), further comprising means configured to cause or effect comparison of C0a, C0b, C0c) with the actual capacitances (C0a', C0b', C0c') and generating a monitoring signal. 24. The method of claim 22 or 23,
A monitoring device ( 1 ), configured as a device ( 1 ) according to claim 11 . 24. The method of any one of claims 22 or 23,
Monitoring device (1), configured to be able to carry out the method according to any one of claims 1 to 4.

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